I need to throw away and replace every part of this setup and I don't have the time, money, energy, or space to do that

Thanks to everyone who has given suggestions for how to fix this. Unfortunately most of them require me standing up for longer than I can manage, so I've mainly just fiddled with settings (since I can do that from my bed).

but when I can, I'll be:
* calibrating the extruder
* trying to clear clogs in the hot-end
* calibrating the z-axis offset (which is a multistep nightmare in this setup)

I need to upgrade the octopi install so I might switch to a newer pi. I have one somewhere, it's just probably up in my office where I can't really get to it (stairs)

installed a USB power blocker to try and fix the undervolting. it didn't work.

So I'm gonna have to find another power supply for that

I'm gonna try cold pulling next because that's easier than getting to the extruder

okay I tried switching to a different USB power supply (5v 2A) with thicker usb cables: No difference, still undervolting.

I also cold-pulled the hot end a few times, to see if that'll help.

the extruder is still difficult to reach

printing another calicat to see if that changed anything

okay I think my extruder is fucked. damn it, that's the most annoying part of this printer to access.